1. Field of the Invention
This application concerns flame retardancy of loosefill insulation materials, especially cellulosic insulation materials. More particularly, the invention relates to flame resistant insulation materials, methods of treating insulation materials to render them flame resistant, compositions for imparting flame resistance to insulation materials, flame and smolder resistant compositions and flame and smolder resistant loosefill insulation materials.
2. Description of the Prior Art
Loosefill insulating materials have been well known in the construction industry for many years and are becoming widely utilized in recent times as a major material for insulation in the housing industry, commercial building industry, as well as in the do-it-your-self home improvement market. The chief advantages of loosefill insulation material are the abundant availability of cellulosic materials such as shredded wood and paper products, the excellent insulation properties of these materials at relatively low costs, and the ability of the material to flow into and fill wall cavities. Unfortunately, the nature of loosefill insulation material, especially cellulosic materials, renders them unacceptable as safe insulation materials in their untreated form due to their high flammability and resultant danger as a fire and smoke hazard.
Accordingly, it has become conventional in the loosefill fiber insulation industry to treat cellulosic material with combustion retardant compounds such as boric acid, ammonium phosphate, aluminum sulfate and the like prior to use. Representative patent literature in this area includes U.S. Pat. No. 3,027,326 to Moffett who discloses the treatment of insulation materials such as shredded wood and shredded paperfluff with a composition consisting of ammonium sulfate, boric acid and potassium alum to reduce the flame and smoldering tendencies of the insulation materials. Other references disclosing the use of phosphate, borates and sulfonates as fire retardants for cellulosic materials include U.S. Pat. No. 2,867,549 to Outterson, U.S. Pat. No. 4,012,507 to Knoepfler and U.S. Pat. No. 4,038,451 to Brown et al.
The addition of ammonium sulfate, boric acid and like compounds to cellulosic insulation increases the density of the material and, accordingly, decreases the insulating value of the insulation. At the same time, the cellulosic insulation industry has encountered difficulties in complying with the federal Interim Safety Standard for Cellulose Insulation issued by the Consumer Product Safety Commission. As a result, chemical loadings as high as 35 to 50 weight percent of retardants based on the weight of the cellulosic material, have been reported as common. At this level the insulative property of the cellulosic material is severely diminished and, in fact, such high loadings reach a point at which further addition of retardants would impair rather than improve the performance of the insulation in combustion tests, i.e. density effects adverse to retardation would predominate over the retarding effects on the material.
The foregoing difficulties result from the fact that it is common to add flame retardant compositions as solids to cellulosic insulation material by mere mixing of the powdered compositions with the cellulosic insulation material in a conventional milling operation. Retention of the retardant powders by the fibrous insulation is not complete and becomes more imperfect as the amounts of added powder increase. During subsequent packaging and handling of insulation material, a greater portion of the powdered flame retardant may settle out from the insulation material and becomes totally ineffective as loadings of powder are increased.
The cellulosic insulation industry has recognized that it would be advantageous to disperse retardants intimately onto insulation material so that the retardants might function more effectively and the quantity of retardants added might be appreciately reduced. Intimate dispersion of retardants into the cellulosic material would also eliminate the need for overloading the insulation material to compensate for the settling problem which would in turn further reduce the required quantity of retardant and improve the insulating value of the material.
Addition of flame retardants from solutions is common practice with materials other than loose-fill insulation. Impregnation of other cellulosic materials from solutions has been widely practiced for many years. Preservation agents such as mold inhibitors, plasticizers and flame retardants have been added to cellulosic materials by spraying aqueous, sometimes resinous, solutions of materials onto the cellulose. An example of one such application of mold inhibitor is found in U.S. Pat. No. 2,713,008 wherein solutions containing 4 to 20% zinc thiocyanate are sprayed onto various cellulosic materials. Application of plasticizing and flame retarding agents by immersing cellulosic material in the solution to be impregnated is disclosed in British Pat. No. 647,582. This patent describes an improvement in the process of treating regenerated cellulose sheets with a combined plasticizer-fire retardant by replacing ammonium thiocyanate with guanadine thiocyanate as the plasticizer-fire retardant. In each of these treatments, the application of large amounts of solution to the cellulosic material was tolerable. The treatment with solution, however, cannot be tolerated by cellulosic insulation materials when the required amounts of solution are large. The time, energy and equipment required for the subsequent necessary drying of the insulation material has been found uneconomic and has seriously restricted the insulation industry's use of treating insulation materials with solutions.